Ayat 5. Call them (adopted sons) by (the names of) their fathers, that is more just with Allah. But if you know not their father’s (names, call them) your brothers in faith and Mawalikum (your freed slaves). And there is no sin on you if you make a mistake therein, except in regard to what your hearts deliberately intend. And Allah is Ever Oft­-Forgiving, Most Merciful.

Tafseer of Surah Al Ahzab (The Confederates) Ayat 05. Call them by (the names of) their fathers: that is just in the sight of Allah. But if ye know not their father´s (names, call them) your Brothers in faith, or your maulas. But there is no blame on you if ye make a mistake therein: (what counts are) the intention of your hearts: and Allah is Oft-Returning, Most Merciful. Freedmen were often called after their master’s name as the "son of so and so". When they were slaves, perhaps their fathers’ names were lost altogether. It is more correct to speak of them as the Mawtd of so and so. But Mawla in Arabic might also imply a close relationship of friendship: in that case, too, it is better to use the right term instead of the term "son". "Brother" is not objectionable because "Brotherhood" is used in a wider sense than "fatherhood", and is not likely to be misunderstood. What is aimed at is to destroy the superstition of erecting false relationships to the detriment or loss of true blood relations. It is not intended to penalize an unintentional slip in the matter, and indeed even if a man deliberately calls another his son or father, who is not his son or father, out of politeness or affections, "Allah is Oft-Forgiving, Most Merciful". It is the action of mischievous parties which is chiefly reprehended, if they intend false insinuations. A mere mistake on their part does not matter.